The present invention relates generally to the manufacture of integrated circuits (IC's). More particularly, the present invention relates to programmable capacitors, and methods therefor, that render the value of the capacitor selectable during manufacturing.
Integrated circuits integrate many discrete functions and components into one "integrated" circuit. One of the reasons integrated circuits presently predominate over discrete component solutions is because of the costs involved in manufacturing, assembling, and testing discrete based circuits. For example, present day microprocessors incorporate more than one million transistors into a square package less than 5 cm on each side. The same number of transistors, discretely and separately placed on a printed circuit board, would require several orders of magnitude more space. Other advantages of integrated circuit technology, which are well known to those skilled in the art, include reliability and cost.
The miniaturization that present day integrated circuit technology, and the benefits that such technology bestows, are applicable to passive component integration as well. When passive devices, e.g., capacitors, resistors, inductors, and the like, are integrated, they are referred to herein as passive component integrated circuits.
In the design of passive thin film integrated circuits, for example, capacitors of different values are needed. By way of example, in the design of a family of filters or terminators, resistors and capacitors are combined in different configurations and values to provide different functionality and performance. In prior art, this is typically accomplished by a custom design and integrated circuit layout configuration for each type of circuit and for each value. This process is time consuming, more prone to errors and less economical.
In the description that follows, an integrated capacitor is selected for discussion. It should be borne in mind, however, that the inventive concepts herein also apply to other types of passive devices, e.g., resistors, inductors, and the like. In the prior art, when an application requires an integrated capacitor having a value that is previously unavailable, a new custom design is necessitated to create an integrated circuit having a capacitor with the desired value. This custom design approach requires a substantial amount of time, effort, and expense since a custom design with specific capacitance values and characteristics must be laid out and verified, the required masks must be created, and manufacturing steps must be tailored to fabricate the required integrated circuit. As can be appreciated from the foregoing, the custom design approach is disadvantageous in view of the great variety of device values required by modern electronic equipment.
In view of the foregoing, what is desired are passive component integrated circuit structures and methods therefor, which can implement a wide range of values in a given single design. This alleviates all the above mentioned limitations of prior art custom design approaches, thereby providing quicker design turnaround time, fewer design errors and a lower manufacturing cost.